1. Field of the Invention
The present invention relates to a printer head using shape memory alloy and a method for manufacturing the same, and more particularly, the present invention relates to a method for manufacturing a printer head using shape memory alloy by a semiconductor process and an etching technique and a printer head using shape memory alloy manufactured by the method.
2. Description of the Related Art
Generally, drop-on-demand (DOD) type printer heads which fire liquid ink only under necessity are most widely used for ink jet printers. Use of such DOD type printer heads has gradually increased in that they require no electric charge or deflection of ink droplets and in that since high pressure is not needed, an easy printing is achieved by immediately firing ink droplets under atmospheric pressure.
Typical firing principles of such printer heads include a heating type firing method using a resistor, a vibration type firing method using a piezoelectric element, and a firing method using shape memory alloy, etc.
A printer head which adopts the heating type firing method generally includes a nozzle plate having a plurality of nozzles, a fluid passage plate coupled onto the nozzle plate and defining an ink storing chamber into which ink is stored, a substrate coupled onto the fluid passage plate and covering the ink storing chamber, and a heating resistor embedded into the substrate.
In an ink firing device of a printer head which adopts a heating type firing method, as shown in FIG. 1, ink is fired as described below.
First, if predetermined voltage is applied to a heating resistor 14, heat is generated. By the heat generated in the heating resistor 14, air contained in ink adjacent the heating resistor 14 is expanded to create air bubbles. By these air bubbles, ink 16 inside an ink storing chamber 10 is forced out through a nozzle 12 to be fired toward a recording medium.
The heating type firing method suffers from defects in that since ink is heated by heat generated in the heating resistor 14, the ink is likely to be chemically degraded, and this degraded ink may be deposited onto an inner surface of the nozzle 12 to clog the nozzle 12. Also, since the heating resistor 14 repeatedly generates heat upon application of voltage, a lifetime of the heating resistor 14 is shortened, and since only water soluble ink should be used, preserving property for a printed document is deteriorated.
A printer head which adopts the vibration type firing method generally includes a nozzle plate having a plurality of nozzles, a fluid passage plate coupled onto the nozzle plate and defining an ink storing chamber into which ink is stored, a substrate coupled onto the fluid passage plate and covering the ink storing chamber, and a piezoelectric element coupled onto the substrate and deforming the substrate while being vibrated when electric power is applied thereto.
In an ink firing device of a printer head which adopts a vibration type firing method, as shown in FIG. 2, ink is fired as described below.
If predetermined electric power is applied to a piezoelectric element 24, the piezoelectric element 24 is vibrated. By vibration of the piezoelectric element 24, volume of an ink storing chamber 20 is momentarily changed, and ink 26 inside the ink storing chamber 20 is forced out through a nozzle 22 to be fired toward a recording medium.
The vibration type firing method using the vibration of the piezoelectric element 24 provides an advantage in that since heat is not used, it is possible to use an ink other than water soluble ink and thereby a greater variety of choices are offered for ink. However, the vibration type firing method is encountered with problems in that since workability for the piezoelectric element is impaired and especially, it is difficult to form the piezoelectric element, productivity is reduced.
FIG. 3 is a cross-sectional view schematically illustrating an ink firing device of a printer head which uses shape memory alloy.
Shape memory alloy 32 which is in a flexurally deformed state is disposed above an ink storing chamber 30. If the shape memory alloy 32 which is in the flexurally deformed state is heated, the shape memory alloy 32 is returned to its original flattened state after a flexurally deformed portion is smoothed out.
As the shape memory alloy 32 is returned to its original flattened state, volume of the ink storing chamber 30 is decreased, and according to this, ink stored in the ink storing chamber 30 is fired through a nozzle 36 to a recording device (not shown).
A printer head using shape memory alloy is classified into a first type wherein several shape memory alloy layers having different phase transformation temperatures and different thicknesses are coupled one with another to be flexurally deformed and a second type wherein a shape limiting body and a shape memory alloy layer are coupled with each other to be flexurally deformed.
Because printer heads of these types employ shape memory alloy of a plate-shaped configuration which has a thickness of 50-1,000 xcexcm and an area of 0.1-10 mm2, power consumption is increased upon heating, heating and cooling times are lengthened to decrease operation frequency, and printing speed is lowered thereby deteriorating practicality of the entire printer head.
Moreover, since the shape memory alloy layer is thick and wide, it cannot be instantaneously heated, and displacement is slowly generated over a relatively long period of time. Accordingly, due to the fact that a generated pressure is reduced, ink may not be fired or may not be properly fired. Also, even in the case that ink is fired, because firing speed of droplets is decreased, wetting may be caused and thereby it is difficult to achieve stable firing of the droplets.
In addition, due to the fact that the shape memory alloy layer has a configuration of a plate which is large and thick and therefore, the entire structure thereof cannot but be enlarged, it is difficult to miniaturize the size of the printer head, integration density of nozzles is diminished and printing resolution is deteriorated.
In other words, in the case that the shape memory alloy is used as taught in the conventional art, the pressure chamber of the printer head must be enlarged such that it has a length of 100-10,000 xcexcm and a width of 50-500 xcexcm. Accordingly, if a pressure chamber of this size is used, the entire structure of the printer head cannot but also be enlarged.
Besides, since the printer head is constructed in that several shape memory alloy layers which are bonded one with another and bent, or a thin plate-shaped shape memory alloy layer and a shape limiting body which are bonded with each other and bent, are attached by bonding to a main body in which an ink storing chamber is defined, it is difficult to manufacture the printer head, and reliability is declined when the shape memory alloy is applied to the ink jet printer head which is required to be vibrated several ten million times.
Also, while an efficient structure is needed to improve ink firing capability, the conventional printer head using shape memory alloy mainly discloses aspects related with a firing method and firing particulars and does not mention structural details of the printer head.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a method for manufacturing a printer head using shape memory alloy which is formed by a semiconductor thin film manufacturing process and has a thin film-shaped configuration and a printer head using shape memory alloy which is manufactured by the method, wherein configurations and sizes of a pressure chamber, a fluid passage and an ink storing chamber as being main components of the printer head are optimized to improve ink firing capability.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for manufacturing a printer head using shape memory alloy, comprising the steps of: preparing a silicon substrate having a flat configuration; thermally oxidizing the silicon substrate to form a pair of silicon dioxide layers on both surfaces of the silicon substrate, respectively; forming a shape memory alloy layer on one of the pair of silicon dioxide layers by a semiconductor thin film forming process; thermally treating the formed shape memory alloy layer; patterning the shape memory alloy layer; patterning the silicon dioxide layers formed on both surfaces of the silicon substrate, respectively; forming an electrode on the shape memory alloy layer to have a desired pattern; forming an insulating layer for protecting the electrode; forming a body of the printer head by etching the silicon substrate on which the electrode and insulating layer are formed; separately forming a nozzle plate into which a plurality of nozzles are formed; forming a fluid passage plate by bonding a photosensitive dry film onto the nozzle plate and patterning the photosensitive dry film; and bonding the nozzle plate and the fluid passage plate onto the body of the printer head. The method can further comprise the steps of: forming an auxiliary plate; applying a photosensitive dry film on the auxiliary plate and patterning the photosensitive dry film; and bonding the auxiliary plate on which the photosensitive dry film is patterned, onto the other of the pair of silicon dioxide layers.
According to another aspect of the present invention, there is provided a method for manufacturing a printer head using shape memory alloy, comprising the steps of: preparing a silicon substrate having a flat configuration; thermally oxidizing the silicon substrate to form a pair of silicon dioxide layers on both surfaces of the silicon substrate, respectively; forming a shape memory alloy layer on one of the pair of silicon dioxide layers by a semiconductor thin film forming process; thermally treating the formed shape memory alloy layer; patterning the shape memory alloy layer; patterning the silicon dioxide layers formed on both surfaces of the silicon substrate, respectively; forming an electrode on the shape memory alloy layer to have a desired pattern; forming an insulating layer for protecting the electrode; applying a photosensitive dry film onto the insulating layer and patterning the photosensitive film; forming a body of the printer head by dry etching the formed silicon substrate; separately forming a nozzle plate into which a plurality of nozzles are formed; and bonding the nozzle plate onto the body of the printer head. The method can further comprise the steps of: forming an auxiliary plate; applying a photosensitive dry film on the auxiliary plate and patterning the photosensitive dry film; and bonding the auxiliary plate on which the photosensitive dry film is patterned, onto the other of the pair of silicon dioxide layers.
According to still another aspect of the present invention, there is provided a method for manufacturing a printer head using shape memory alloy, comprising the steps of: preparing a silicon substrate having a flat configuration; thermally oxidizing the silicon substrate to form a pair of silicon dioxide layers on both surfaces of the silicon substrate, respectively; forming a shape memory alloy layer on one of the pair of silicon dioxide layers by a semiconductor thin film forming process; thermally treating the formed shape memory alloy layer; patterning the shape memory alloy layer; patterning the silicon dioxide layers formed on both surfaces of the silicon substrate, respectively; forming an electrode on the shape memory alloy layer to have a desired pattern; forming an insulating layer for protecting the electrode; applying a photosensitive dry film onto the insulating layer and patterning the photosensitive film to define a body of the printer head; separately forming a nozzle plate into which a plurality of nozzles are formed; bonding the nozzle plate onto the body of the printer head; and dry etching the silicon substrate. The method can further comprise the steps of: forming an auxiliary plate; applying a photosensitive dry film on the auxiliary plate and patterning the photosensitive dry film; and bonding the auxiliary plate on which the photosensitive dry film is patterned, onto the other of the pair of silicon dioxide layers.
According to yet still another aspect of the present invention, there is provided a printer head using shape memory alloy comprising: a substrate; space parts defined at both sides of the substrate; a vibrating plate formed on the substrate such that it covers the space parts, to be vibrated while being changed in its contour depending upon temperature variation, the vibrating plate including a shape memory alloy layer and a silicon dioxide layer; an electrode formed on the vibrating plate to have a desired pattern; an insulating layer formed to protect the electrode; an ink storing chamber formed between the space parts of the substrate for storing ink; a pressure chamber defined on the vibrating plate for containing ink, the pressure chamber discharging ink by vibration of the vibrating plate; a fluid passage plate formed at a side of the pressure chamber; a fluid passage formed by the fluid passage plate for allowing the ink stored in the ink storing chamber to flow into the pressure chamber; a nozzle plate attached onto the fluid passage plate for allowing ink to be fired in the form of droplets when the vibrating plate is vibrated; and a plurality of nozzles formed in the nozzle plate for firing ink to a recording device.